Austenitic stainless steel bearing Nb compositional and plastic deformation effects

Austenitic stainless steel has excellent ductility. Consequently, it has capability for heavily cold deformation, despite its high strength and high work hardening ability. Austenitic stainless steel predominantly contains high levels of chromium and nickel. Additional elements may be added to enhance performance. The target of this paper is to melt and cast several austenitic stainless steel alloys with different Nb contents. Furthermore the effects of the chemical composition on strength as well as the effect of cold rolling on the creation of induced martensite phase are also studied. The microstructural investigation shows that grain coarsening was observed on the as-cast structure accompanying with thick grain boundary carbides along with carbide agglomerations at the triple points. Hot deformation diminishes the grains as well as the carbide films surrounding the grains. Solution treatment creates austenitic grains free of grain boundary carbides. Cold deformation creates highly elongated grains associated with wavy pancaked structure. Numerical modeling extensively used to detect the proof strength at high temperatures (up to 600 °C). The detected proof strength decreases drastically by raising the deformation temperatures. Nb was found to increase the proof strength even at high temperatures. The measured mechanical properties of the alloys under investigation are higher than that of detected ones by Kimura model, where the model did not pay attention to the Nb effect. Elliason model for the flow curve of different alloys has been extensively studied and applied. The detected results have been verified by the microstructural changes during deformation.